1. Field of the Invention
The present invention relates generally to recording mediums such as disk, tape and drum and to methods of recording and reproducing therefor, and more particularly, to a magneto-optical disk and a recording/reproducing method therefor.
2. Description of the Related Art
Various storage mediums such as compact disk, mini disk, digital video disk and video tape are provided today. The data formats and recording capacities of these storage mediums are specified by JIS (Japanese Industrial Standards) or the like. On the other hand, recent developments in various elements in the field of recording/reproducing and pickup technology have enabled a significant increase in the recording capacities.
It would be difficult to secure compatibility between recording/reproducing apparatuses for a recording medium if the specification of the recording medium is changed every time rapid progress in the technology enables a further increase in recording capacity. If we give up the compatibility, however, a reproducing apparatus fabricated according to a new specification may not be able to reproduce signals from a storage medium according to an old specification, which gives rise to inconvenience to a user. Meanwhile, in order to secure compatibility, the cost to produce a recording/reproducing apparatus increases.
It is therefore one object of the invention to provide a storage medium permitting recording at a high density almost without having to change the specification in the future and a recording/reproducing method therefor.
Another object of the invention is to provide a storage medium which makes easier improvement of a recording/reproducing apparatus in association with increase in the recording density, and a recording/reproducing method therefor.
A storage medium according to one aspect of the invention includes a recording area and correlation information. The correlation information is recorded in the recording area, and indicates the correlation between recording densities and recording/reproducing conditions each necessary for a recording/reproducing apparatus to record and/or reproduce a signal at a recording density. The correlation information preferably includes a table. The table has a plurality of recording densities and a plurality of recording/reproducing conditions each necessary for a recording/reproducing apparatus to record and/or reproduce a signal at a corresponding recording density. The storage medium preferably further includes a plurality of recording unit regions for recording prescribed data. The recording densities permit the prescribed data to be equally allocated to the plurality of recording unit regions. The recording region preferably includes a spirally formed track. The correlation information is recorded on an innermost and/or outermost part of the spiral track. The storage medium preferably further includes identification information recorded in the recording area to identify a recording density at which a signal has been recorded. Note that the recording/reproducing conditions are preferably pre-stored in a memory or the like in the recording/reproducing apparatus.
According to another aspect of the invention, a method of recording a signal in a storage medium including a recording area and correlation information recorded in the recording area and indicating correlation between recording densities and recording conditions necessary for a recording apparatus to record a signal at the recording densities includes the steps of loading the correlation information from the storage medium, determining a recording density based on the loaded correlation information, and setting a recording condition based on the determined recording density. The recording apparatus preferably has a plurality of first recording conditions which are necessary for recording a signal and can be selectively set. The correlation information includes a table having a plurality of recording densities and a plurality of second recording conditions corresponding to the plurality of recording densities and each necessary for the recording/reproducing apparatus to record a signal at a corresponding recording density. The determination step includes the steps of comparing the plurality of first recording conditions with the plurality of second recording conditions loaded in the table, selecting a second recording condition in coincidence with the first recording condition among the plurality of second recording conditions based on the result of the comparing step, and specifying a recording density corresponding to the second recording condition selected from the plurality of recording densities. Further preferably, the above method further includes the step of interrupting recording of a signal if none of the second recording conditions is in confidence with each of the first recording conditions based on the result of the comparison step. The determination step preferably includes the steps of comparing the plurality of first recording conditions with the plurality of second recording conditions in the loaded table, selecting a plurality of second recording conditions in coincidence with the first recording conditions from the plurality of second recording conditions, displaying a plurality of recording densities corresponding to the selected plurality of second recording conditions, and specifying one of the displayed plurality of recording densities in response to a specification by the user. The setting step preferably changes the frequency of a synchronizing clock signal used to record a signal in response to the determined recording density. The recording apparatus preferably further includes a frequency divider for generating a synchronizing clock signal. The changing step changes the dividing ratio of the frequency divider depending upon the determined recording density. The storage medium preferably further includes a plurality of recording unit regions for recording prescribed data. The recording densities permit the prescribed data to be equally allocated into the plurality of recording unit regions.
According to yet another aspect of the invention, a method of reproducing a signal from a storage medium including a recording area, correlation information recorded in the recording area and indicating correlation between recording densities and reproducing conditions necessary for a reproducing apparatus to reproduce a signal at the recording densities, and identification information recorded in the recording area for identifying a recording density at which a signal has been recorded includes the steps of loading the correlation information and identification information from the storage medium and setting the reproducing apparatus to a reproducing condition based on the loaded correlation information and identification information. The setting step preferably changes the frequency of a synchronizing clock signal used for reproducing a signal depending upon the recording density of the loaded identification information. The reproducing apparatus preferably further includes a frequency divider for generating a synchronizing clock signal. The changing step changes the dividing ratio of the frequency divider depending upon the recording density of the loaded identification information.
Since the storage medium includes the correlation information indicating correlation between recording densities and recording/reproducing conditions, a new type recording/reproducing apparatus employing a new technique may record/reproduce a signal to/from the medium at an appropriate recording density, and an old type recording/reproducing apparatus may record/reproduce a signal to/from the medium at a conventional recording density. Therefore, a storage medium capable of recording at a high density almost without changing the specification is provided. As a result, a recording/reproducing apparatus can be prevented from rapidly becoming out of date in association with changes in the specification, and can flexibly suit user""s preference.
Since the recording densities employed permit prescribed data to be equally allocated into a plurality of recording unit regions, a circuit configuration for distributing the data may be simplified.
Furthermore, since the frequency of a synchronizing clock signal is changed depending upon the determined recording density, the recording density may be improved even if the speed of the storage medium relative to the pickup is fixed. In addition, according to the above-described method, the dividing ratio of the frequency divider is changed depending upon the determined recording density, and therefore the frequency of the synchronizing clock signal may be easily changed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.